1. Field of the Invention
This invention relates to a semiconductor device and a manufacturing method thereof.
2. Description of the Related Art
There has been a demand for thinner semiconductor devices as electronic equipment becomes thinner. However, if a semiconductor substrate in a wafer state is made too thin, the semiconductor substrate is damaged in a semiconductor manufacturing process in which integrated circuits are formed on a front surface of the semiconductor substrate in the wafer state. Thus, a technique has been developed wherein after the integrated circuits are formed on the front surface of the semiconductor substrate in the wafer state having a predetermined thickness, a rear surface opposite to the surface on which the integrated circuits are formed is ground to reduce the thickness of the semiconductor substrate. Jpn. Pat. Appln. KOKAI Publication No. 2001-230224 discloses such a method of manufacturing a conventional semiconductor device. This prior document discloses a method which comprises: grinding a rear surface of a semiconductor substrate in a wafer state in which integrated circuits and external connection electrodes are formed on a front surface side thereof; forming a protective film made of a resin on the rear surface of the semiconductor substrate in the wafer state; and cutting, after passing through predetermined subsequent steps, the semiconductor substrate in the wafer state to obtain a plurality of semiconductor devices.
In the semiconductor device obtained by the conventional manufacturing method described above, the rear surface of the semiconductor substrate is ground to form minute and acutely-angled irregularities on the rear surface of the semiconductor substrate, so that even if a protective film made of a resin is formed on the minute and acutely-angled irregular surface, it is difficult to ensure that the resin is filled into the inner part of the minute and acutely-angled concave portions. As a result, there is a problem that cracks may be caused in the rear surface of the semiconductor substrate due to the fact that the inner parts of the minute and acutely-angled concave portions are not covered with the protective film.